Abidjan, Ivory Coast (CNN) -- The three leaders representing a West African bloc will return to Ivory Coast next Monday to again try to defuse an escalating political crisis sparked by self-declared President Lauren Gbagbo's refusal to cede power.
Tension in Ivory Coast increased Wednesday with a call by a key backer of Gbagbo for supporters to "liberate" the Golf Hotel in Abidjan, where President-elect Alassane Ouattara has his headquarters.
Youth and Employment Minister Charles Ble Goude said on state television RTI that Gbagbo's supporters should "liberate this place with your bare hands" after January 1st.
Ouattara is residing at the U.N.-protected hotel and using it as his headquarters.
In the television broadcast, Ble Goude said Ouattara supporters were taunting Gbagbo's government by calling for international intervention in the political standoff.
The international community -- including the United States, the United Nations, the African Union and the European Union -- recognize Ouattara as the president-elect of Ivory Coast, based on the results of the November runoff election certified by the country's Independent Electoral Commission and international observers.
Earlier Wednesday, Presidents Yayi Boni of Benin, Ernest Bai Koroma of Sierra Leone and Pedro Pires of Cape Verde met with President Goodluck Jonathan of Nigeria, which chairs the Economic Community of West African State (ECOWAS), a spokesman for the group told CNN.
No details of the talks with the Nigerian president were immediately available.
The three presidents traveled to Ivory Coast on Tuesday but failed to persuade Gbagbo to step down, even though ECOWAS has threatened military intervention.
The political stalemate has led to violence, with scores of people dying in the aftermath of the vote.
In anticipation of the possibility of further unrest, the U.S. State Department has ordered the departure of family members and non-emergency personnel at the U.S. Embassy in Abidjan.
The order, originally announced December 20 and repeated Wednesday, also said the embassy's Consular Section in Abidjan would only handle emergency services for U.S. citizens.
Also Wednesday, a one-time aide to former U.S. President Bill Clinton resigned as Gbagbo's attorney, saying in a letter to Ivory Coast Ambassador Charles Koffee that efforts to arrange a phone call between Gbagbo and U.S. President Barack Obama had been thwarted by unidentified officials in Gbagbo's government.
Lanny Davis, who served as special counsel to Clinton, said in the letter that he had urged Gbagbo to invite "an independent international investigation of his claims of electoral fraud and violence, and to respect the results of that review, as a path to the peaceful and mediated resolution of this crisis."
The proposed phone call from Obama, which Davis said was being arranged by a senior State Department official, would have presented Gbagbo "with options for a peaceful resolution, that would avoid further bloodshed and be in the best interests of his country and the people of the Ivory Coast," according to the letter by Davis.
"Unfortunately, as you know, the decision was made in Abidjan not to allow President Obama's call to be put through to Mr. Gbagbo, despite my repeated objections to that decision," Davis wrote in the letter. "Nor have I been able to reach Mr. Gbagbo directly myself to offer him this advice, despite repeated requests, as recently as the last twenty-four hours."
Davis' letter said he would continue pushing for dialogue and mediation to bring a peaceful resolution of the situation, "but for the reasons expressed above I will no longer be able to do so as a representative of your government."
Earlier, French Foreign Ministry spokesman Bernard Valero told reporters in Paris that only ambassadors sent with the approval of Ouattara would be recognized by European Union countries.
According to the French Foreign Ministry, European Union representatives agreed last week on this element as part of a unified approach to the situation in Ivory Coast. The new Ivorian ambassador to France has been named, Valero said, and was in the process of being approved.
"In waiting for the finalization of this procedure, we are working with the Ivory Coast Embassy in Paris... in agreement with the legitimate authorities of that country," Valero said.
In another symbolic move, U.N. Secretary General Ban Ki-moon on Wednesday accepted the credentials of Youssoufu Bamba, the U.N. ambassador appointed by Ouattara.
Gbagbo's government has threatened to expel ambassadors of countries that recognize Ouattara's appointees, according to spokesman Ahoua Don Melo.
Speaking on national television, he said the move would be a measure of reciprocity and seemed to take aim at France and Belgium, which has said it will recognize Ouattara's appointee.
Gbagbo advisor Abdon Bayeto said Wednesday that there was an "international plot" against the incumbent president, and urged other nations to recognize the election results as declared by the country's Constitutional Council -- which said that Gbagbo had won.
"The solution is to come and verify yourself," he said.
It's unclear if ECOWAS intends to make good on its threat to use military means against Ivory Coast if Gbagbo does not leave, or what kind of force would be used. It has intervened before in Liberia and Sierra Leone.
Bayeto warned that his nation would not be trampled so easily.
A convoy of Bangladeshi peacekeepers came under attack Tuesday in Abidjan, the United Nations said. One soldier was slashed in the arm by a machete and a U.N. vehicle was burned.
The African Union has suspended Ivory Coast from the organization "until such a time the democratically elected president effectively assumes state power." And the World Bank has halted lending and disbursing funds to Ivory Coast and has closed its office in the country.
The U.S. Department of Defense currently has a group in Abidjan looking into the possible evacuation of U.S. citizens. State Department spokesman Mark Toner confirmed it was a "small DoD assessment team on the ground at the embassy in Abidjan to help with contingency planning."
More than 15,000 refugees have fled for neighboring Liberia, according to the U.N. High Commissioner on Refugees, a large number of them women and children.
CNN's Moni Basu, Alanne Orjoux, Jill Dougherty, Elise Labott and Richard Roth and journalist Eric Agnero contributed to this report.